The present invention relates to carpet backing compositions. More particularly, the present invention relates to extruded carpet backing materials used to provide a durable, highly flexible carpet backing capable of being thermoformed. Still more particularly, the present invention relates to carpet constructions, preferably including a tuft, means, such as a scrim, for retaining the tuft, and an extruded thermoplastic barrier coating as the carpet backing therefor.
While carpets are generally manufactured by a number of methods, processes such as tufting and needle punching have become quite popular in the last few years. In particular, the majority of carpeting manufactured today is produced by the tufting process. Tufted carpets are composite structures in which the face fiber forming the pile, i.e., the surface of the carpet, is needled through a primary backing and the base of each tuft extends through the primary backing and is exposed on the bottom surface of the primary backing.
The basic manufacturing approach to the commercial production of tufted carpeting is to start with a woven scrim or primary carpet backing and to feed this into a tufting machine or a loom. The carpet face fiber is needled through and embedded in the primary carpet backing thus forming a tufted base or griege goods. Griege goods are typically backed with an adhesive coating in order to secure the face fiber to the primary backing. In order to reduce costs, some carpet often receives only a latex adhesive coating as the backing. Higher cost carpet often receives both a secondary backing and a latex adhesive coating.
The application of the latex adhesive coating involves preparing griege goods by stitching a primary carpet backing material with face fiber in a manner so as to form on the top surface of the material a pile composed of numerous closely spaced, up-standing loops of yarn. Thereafter, the bottom surface of the thus formed griege goods is coated with a latex polymer binder such as a styrene-butadiene copolymer. The coated griege goods are then passed through an oven to dry the latex adhesive coating to bond the face fibers to the primary backing which causes the bonding of and which is the principal reason for adding the latex binder.
In another method, such tufted carpets have been manufactured by processes which generally comprise composite structures in which tufts, or bundles of carpet fibers are introduced (such as by stitching) into a primary backing or scrim, such as a woven or non-woven fabric. A secondary backing or coating of thermoplastic material is then applied to the underside of the carpet construction in order to securely retain the tufted material in the primary backing. This secondary backing not only dimensionally stabilizes this construction but also provides greater abrasion and wear resistance, and serves as the adhesive for the barrier coating.
The face fiber or yarn used in forming the pile of a tufted carpet is typically made of any one of a number of types of fiber, such as nylon, acrylics, polypropylene, polyethylene, polyamides, polyesters, wool, cotton, rayon and the like.
Primary backings for tufted pile carpets are typically woven or non-woven fabrics made of one or more natural or synthetic fibers or yarns, such as jute, wool, polypropylene, polyethylene, polyamides, polyesters, and rayon. Films of synthetic materials, such as polypropylene, polyethylene and ethylene-propylene copolymers may also be used to form the primary backing.
Likewise, secondary backings for tufted pile carpets are typically woven or non-woven fabrics made of one or more natural or synthetic fibers or yarns. Preferably, secondary backings for tufted pile carpets are open weave or leno weave, i.e., tape yarn in the warp direction and spun staple fiber in the fill direction. The spun staple fiber is more costly but desirable to increase adhesion between the backing and the latex adhesive.
Another commercially important carpet manufacturing process is needle punching. In this process the carpet fibers are punched by a series of barbed needles, which causes them to mechanically interlock and form a non-woven loose fabric structure. In the known processes, the problem of fiber loss is always present. In most cases, a back coating is employed to reduce fiber loss and to also provide dimensional stability and body. The problem of such fiber loss is particularly acute in connection with automotive carpeting where wear is generally concentrated into limited areas. Automotive carpet is subjected to sliding and other forces, which have resulted in excessive fiber loss therein.
The method utilizing a latex polymer binder for making carpet is used in 80 to 90% of all carpet made in the United States. This carpet-making method has disadvantages in that it requires a drying step and thus an oven to dry the latex polymer binder. The drying step increases the cost of the carpet and limits production speed. Furthermore, it has recently been reported that latex adhesive compositions may generate gases that may be the cause of headaches, watery eyes, breathing difficulties and nausea, especially when used in tightly sealed buildings. See Herligy, The Carpet and Rug Industry, October 1990. In addition, overheating of the carpet may occur during drying of the latex, which in turn may affect the shade, or color of the carpet.
Consequently, carpet manufacturers have been attempting to develop a new approach for the preparation of tufted carpets. One new approach is the preparation of tufted carpets with a hot-melt adhesive composition instead of a latex composition.
Hot-melt adhesives are amorphous polymers that soften and flow sufficiently to wet and penetrate the backing surfaces and tuft stitches of carpets upon application of sufficient heat. Furthermore, hot-melt adhesives tend to adhere to the backing surfaces and/or tuft stitches. That is, hot-melt adhesives stick to backing surfaces and tuft stitches.
By the use of hot-melt adhesive, the necessity of drying the composition after application is eliminated and further, when a secondary backing material is desired, it can be applied directly after the hot-melt composition is applied with no necessity for a drying step.
Application of a hot-melt composition is generally accomplished by passing the bottom surface of the griege goods over an applicator roll positioned in a reservoir containing the hot-melt composition in a molten state. A blade is ordinarily employed to control the amount of adhesive which is transferred from the application roll to the bottom surface of the structure. After application of the hot-melt composition to the bottom surface of the griege goods, and prior to cooling, the secondary backing, if desired, is brought into contact with the bottom surface, and the resulting structure is then passed through nip rolls and heated.
The activation temperature of a hot-melt adhesive, i.e., the temperature at which the adhesive softens and flows sufficiently to wet and penetrate the backing surfaces and tuft stitches, is below the temperature at which the backing and face yarns melt or otherwise distort. Otherwise, the backing and face yarns may suffer other damage due to heating.
Hot-melt adhesives also must have low enough viscosities at temperatures employed in finishing to achieve good wetting of the backings and sufficient encapsulation of tuft stitches to make the tuft yarns resistant to pull-out, pilling and fuzzing. In addition, for commercial practice, economics of a carpet manufacturing process utilizing hot-melt adhesive must be at least as good as those of conventional latex lamination techniques which remain the dominant lamination process in commercial carpet manufacture.
A number of hot-melt adhesives and processes using the hot-melt adhesive have been proposed for use in carpet lamination. For example, U.S. Pat. No. 3,551,231, issued Dec. 29, 1970 to Smedberg, discloses a hot-melt adhesive carpet lamination process in which molten adhesive consisting of an ethylene-vinyl acetate copolymer and, optionally, waxes (e.g., microcrystalline and polyethylene waxes), fillers (e.g., calcium carbonate), resin extenders (e.g., dicyclopentadiene alkylation polymers) and antioxidant is applied to a tufted primary backing and then a secondary backing is contacted with the molten adhesive under pressure after which the assembly is cooled to solidify the adhesive.
U.S. Pat. No. 3,583,936, issued Jun. 8, 1971 to Stahl, discloses a hot-melt adhesive for tufted carpet lamination comprising about 10-35 weight percent ethylene copolymer comprising about 60-85 weight percent ethylene, and about 15-40 weight percent lower vinyl ester, acrylate or methacrylate; about 10-25 weight percent wax, such as microcrystalline petroleum, polyolefin, or paraffin wax having a melting point sufficient to give an adhesive composition with a softening point greater than 190.degree. F.; and about 50-70 weight percent resin extender composed of a base resin prepared from reactive olefins and diene monomers of 5-7 carbons.
The hot-melt compositions are selected for their adhesive properties. That is, the hot-melt composition may be selected for their suitability in adhering the tufts of face yarn to the primary backing and to adhere the secondary backing to the primary backing. Such compositions are generally amorphous or substantially non-crystalline due to the adhesive properties of such polymers.
For example, U.S. Pat. No. 3,982,051, issued Sep. 21, 1976 to Taft et al., discloses a carpet containing a hot-melt composition of ethylene copolymer, atactic polypropylene and vulcanized rubber. The atactic, substantially non-crystalline, polypropylene used in the hot-melt composition may be obtained as a by-product from the preparation of substantially crystalline, isotactic, polypropylene. Atactic polypropylene is particularly suitable as a hot-melt composition due to its adhesive nature whereas isotactic polypropylene is not particularly suitable as a hot-melt composition due to its lack of adhesive properties.
While the hot-melt compositions and processes heretofore known are considerably simpler than the latex process, the preparation of carpets of non-uniform quality has, at times, been encountered. Specifically, such carpets using hot-melt adhesives cannot, with reproducible consistency, be prepared with high scrim bonds (force required to remove the secondary backing from the finished carpet), high tuft pull strength (force required to pull one of the tufts out of the carpet), and high fuzz resistance (an indication of the individual carpet yarns to fuzz and form pills). Thus, while such hot-melt compositions are appealing from a standpoint of cost, speed and safety, some difficulties have been encountered in preparing completely satisfactory carpet. See U.S. Pat. No. 3,551,231, issued Dec. 29, 1970 to Smedberg.
Thus, conventional carpet and carpet manufacturing processes have inherent problems including the compositions employed therein. Specifically, the adhesives used to adhere the tufts of face fiber to the primary backing and to adhere the secondary backing to the primary backing include compositions which require lengthy drying times. Drying adds costs and slows down the manufacturing process. In addition, the latex compositions may produce noxious off-gases that create health hazards. Likewise, many of the hot-melt compositions conventionally employed in the manufacture of carpet do not result in reproducible consistency regarding scrim bonds, tuft pull strength and fuzz resistance. Finally, and most importantly, the use of conventional latex adhesives and hot-melt adhesives prevent carpet from being recycled.
As an improvement over the previously used coatings as the secondary carpet backing, and in an attempt to provide a sound and thermal barrier in connection with automotive carpeting, attempts have been made to apply various thermoplastic resin layers to carpeting. U.S. Pat. No. 3,525,662, for example, teaches the use of a coating of thermoplastic material comprising a mixture of polyolefin and low viscosity saturated hydrocarbon such as petroleum wax. The patentee claims that this inclusion of low viscosity material increases the speed of processing as well as the wear characteristics of his final carpet product, which is said to be particularly intended for use in automotive carpeting.
Subsequently, Collins and Aikman Corporation developed a calcium carbonate-loaded ethylene/vinyl acetate copolymer system which had many desirable properties for use in such systems. U.S. Pat. No. 3,551,231 discloses the application of a hot melt adhesive blend of ethylene/vinyl ester copolymer, petroleum wax, and a thermoplastic resin, in this case in conjunction with the application of a critical degree of pressure on the tufted structure during contact with the adhesive applicator roll.
Further developments in connection with secondary carpet backings include that in U.S. Pat. No. 3,390,035, which discloses the use of a molten thermoplastic adhesive material including an ethylene/vinyl acetate copolymer, wax, and optionally a thermoplastic resin other than the ethylene copolymer.
In U.S. Pat. No. 3,684,600 a low viscosity pre-coated adhesive is disclosed for application to the backside of a tufted carpet structure prior to the application of the hot melt adhesive. The backside adhesive disclosed in that patent again contains ethylene/vinyl ester copolymer, in this case along with low molecular weight, low-density polyethylene, microcrystalline wax, aliphatic thermoplastic hydrocarbon resin, dicyclopentadiene alkylation polymer, antioxidant, and filler.
Similar such compositions are disclosed in U.S. Pat. Nos. 3,583,936 and 3,745,054, and improvements on these compositions are alleged to be included in U.S. Pat. No. 3,914,489 which discloses such carpet backings including ethylene/vinyl ester copolymer, a hydrocarbon resin having a prescribed softening point and viscosity, and optionally also low molecular weight ethylene homopolymer, paraffin wax, antioxidant, and filler.
U.S. Pat. No. 3,982,051 discloses yet another carpet hot melt composition, in this case including ethylene/vinyl acetate copolymer, atactic polypropylene, and vulcanized rubber.
Neither the latex adhesive based carpet nor the hot-melt adhesive based carpet may be easily recycled. Thus, large quantities of carpet trimmings and scrap, produced during the manufacture of carpet, and used carpet are sent to landfills. Consequently, carpet manufacturers spend a substantial sum on landfill costs.
Other patents teach the use of extruded carpet backing in automotive applications. These patents are directed to providing a form and insulation for the carpet. U.S. Pat. No. 4,508,771 to Peoples, Jr. et al., issued on Apr. 2, 1985 is directed to such a carpet backing composition. U.S. Pat. No. 5,876,827 to Fink et al., issued on Mar. 2, 1999 is directed to pile carpet, which may be recycled, and methods of manufacturing such. U.S. Pat. No. 5,221,394 to Epple et al., issued on Jun. 22, 1993 is directed to a method for manufacturing backed, pressure-adherent industrial carpeting. U.S. Pat. No. 5,240,530 to Fink, issued on Aug. 31, 1993 is also related to the same area. U.S. Pat. No. 5,474,829 to Woosley, issued on Dec. 2, 1995 also provides some background information. For the purposes of the U.S. prosecution only, these patents are incorporated herein by reference in their entirety.
In one particular process for the manufacture of automotive carpets, nylon fibers are tufted into a PET (polyethylene terephthalate) non-woven sheet. An LDPE (low density polyethylene) is used to pre-coat carpet backing via extrusion. In some applications where pre-colored nylon fibers are utilized, LDPE has proven to be less than satisfactory in this application. Since xe2x80x9cNylon 6,6xe2x80x9d has been replaced by xe2x80x9cNylon 6xe2x80x9d, LDPE has started showing poor performance, for example, poor abrasion resistance and weak adhesion. Carpet manufacturers have been getting such claims from auto manufacturers that fibers have been pulled off more easily from the carpet installed in the vehicle when a driver rubs his or her feet against the carpet. These complaints were attributed to the poor performance of LDPE as the adhesive layer. When Nylon 6,6 is used in the carpet, a dying process is required. The dying process includes subjecting the carpet to washing and drying processes, thus providing xe2x80x9cloosenedxe2x80x9d fiber face to be coated with polymer melt. Hence, washed and dried fibers facilitate carpet backing, such as LDPE melt, to easily penetrate into the fiber face. Thus, high MFR has been a major requirement for the pre-coating material.
However, Nylon 6 is pre-colored and thus, does not require a dying process. Therefore, the washing and drying steps are not included and the fibers exposed from the primary (PET) backing may be too tight for the polymer melt to penetrate. The high MFR is not the required property any more. In order to qualify as a pre-coating material, new materials with better-defined requirements have been sought. The crystallization kinetics of polymer melt applied to the carpet fiber became a critical factor as compared to the MFR.
Accordingly, there is a need for carpet backing compositions that show acceptable properties in this application. The formulation needs to provide a sheet of material that completely xe2x80x9cwetsxe2x80x9d the carpet backing when applied through extrusion. This includes improved performance in both MFR and crystallization properties. Additionally, the sheet should result in acceptable abrasion and adhesion properties.
From the above background, it is quite apparent that there is need in the art for an improved carpet and method for producing carpet as well as a method for recycling carpet.
The present invention relates to an improved carpet, method for producing a carpet and method for producing a secondary carpet backing that overcomes many of the problems associated with conventional carpet and carpet manufacturing processes.
Specifically, a carpet is disclosed having at least a primary backing, tufts of carpet fibers protruding from a top surface of the primary backing, a secondary backing of an extruded sheet integrally fused to the primary backing.
Also disclosed is a process for manufacturing automotive carpet including at least contacting a bottom surface of a primary backing having tufts of carpet fibers protruding from its top surface with an extruded sheet of thermoplastic polyolefin polymers and modifiers, at a temperature sufficiently high to integrally fuse the extruded sheet to the bottom surface of the primary backing.
Another object of the present invention is to provide a process for manufacturing a carpet having a primary backing, tufts of carpet fibers protruding from a top surface of the primary backing, and a secondary backing integrally fused to a bottom surface of the primary backing. The secondary backing comprises at least 10% syndiotactic polypropylene.
In another embodiment of the present invention, the carpet backing composition comprises (a) from about 50-80% by weight of a polypropylene homopolymer or copolymer, (b) not less than 10% by weight syndiotactic polypropylene, and (c) not greater than 35% by weight impact modifier.
In a preferred mode, this carpet backing composition has a melt flow rate of at least 150 grams/10 min. at 230xc2x0 C. Most preferably, the composition has a melt flow rate of about 300 grams/10 min. at 230xc2x0 C.
These and other objects and features will be apparent from the detailed descriptive material that follows.